[gdal-dev] Mosaicking Orthos

[Chaitanya kumar CH]

Zoltan,

Have you tried the nearblack GDAL utility on the original 176 images?
http://www.gdal.org/nearblack.html

On Wed, Feb 16, 2011 at 5:25 PM, Zoltan Szecsei <zoltans at geograph.co.za>wrote:

> On 2011-02-16 12:20, Zoltan Szecsei wrote:
>
>> Hi All,
>> I've built a vrt with 176 images.
>>
>> I now need to mosaic this whole area into roughly 5 x 5 ortho images.
>>
>> How can I force the white edges into background of the overlapping orthos?
>> I'm a little cautious of simply (finding a way to) making "white"
>> transparent as it is only the white on the edges that need to be
>> backgrounded.
>>
>
> Hi again,
> Since the above post, I have tried different ways to set nodata, but to no
> avail - I still get the white edges:
> (see jpeg sent with my original post)
>
> gdalbuildvrt -addalpha -hidenodata -input_file_list files
> 177_untiled_orthos_nodata.vrt
> gdalbuildvrt -srcnodata "0 0 0"  -addalpha -hidenodata -input_file_list
> files 177_untiled_orthos_blk.vrt
> gdalbuildvrt -srcnodata "255 255 255"  -addalpha -hidenodata
> -input_file_list files 177_untiled_orthos_white.vrt
>
> How should I be masking out the nodata (or even white pixels) so that when
> I mosaic a bunch of tiffs together, I dont get the white stripes in the
> resulting image?
>
> Using GDAL 1.7.3, released 2010/11/10 on Ubuntu 10.04
> Viewing with Quantum GIS - 1.6.0-Trunk on Ubuntu 10.04 (same box).
> ...but running the whole lot in xterms with Xming & putty from my WinVista
> box.
>
>
> Regards,
>
> Zoltan
>
>
>
>
> --
>
> ===========================================
> Zoltan Szecsei PrGISc [PGP0031]
> Geograph (Pty) Ltd.
> P.O. Box 7, Muizenberg 7950, South Africa.
>
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>
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-- 
Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/
+91-9494447584
17.2416N 80.1426E
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